1. Field of the Invention
The present invention relates to an image forming apparatus such as a printer, a multi function peripheral (MFP), a facsimile etc., and, more particularly to an image forming apparatus that includes latent image-carrying members that bear latent images on an endlessly moving surface and a latent image writing unit that can move between a writing operation position for carrying out a writing operation to write the latent images on the surface and a retracting position when the writing operation is not carried out.
2. Description of the Related Art
In an existing electronographic image forming apparatus, a latent image writing unit such as a laser writer, which carries out optical scanning using a laser beam, writes latent images on latent image-carrying members such as uniformly charged photosensitive drums. Depending on a layout inside the image forming apparatus, the latent image writing unit becomes a hindrance, thus worsening maintainability of the latent image-carrying members and various peripheral devices such as developers that are arranged in the periphery of the latent image-carrying members.
In an image forming apparatus that is disclosed in Japanese Patent No. 2849978, the latent image writing unit is supported by an opening and closing cover that can be opened and closed with respect to a fixed cover that is a portion of a chassis of the image forming apparatus. Releasing the opening and closing cover significantly separates the latent image writing unit from the latent image-carrying members. Using the structure mentioned earlier enables to retract, along with a release of the opening and closing cover, the latent image writing unit from a position opposite the latent image-carrying members and to expose to outside the latent image-carrying members and the peripheral devices. Thus, maintainability of the latent image-carrying members and the peripheral devices can be enhanced.
However, in the image forming apparatus mentioned earlier, the opening and closing cover jolts against the fixed cover, thus causing occurrence of an error in relative positions of the latent image writing unit that is supported by the opening and closing cover and the latent image-carrying members that are supported by the fixed cover. Occurrence of the error reduces writing position accuracy of the latent image writing unit.
To overcome the drawback, the present applicant suggested an image forming apparatus that is disclosed in Application Filing No. 2006-008716 (hereinafter, “prior application”). To explain specifically, in the image forming apparatus disclosed in the prior application, a standard position member, which is included in the latent image writing unit that is held by the opening and closing cover, is biased by a biasing unit at the writing operation position when the opening and closing cover is closed and the standard position member is caused to touch a positioning unit inside the image forming apparatus. Due to this, a position of the latent image writing unit can be precisely decided with respect to the latent image-carrying members that are supported by the fixed cover inside the image forming apparatus. Thus, reduction of the writing position accuracy of the latent image writing unit can be curbed.
However, in the image forming apparatus that is disclosed in the prior application mentioned earlier, forcefully closing the opening and closing cover with respect to the fixed cover increases a shock when the standard position member collides with the positioning unit and is likely to cause significant warping of the opening and closing cover and the standard position member. If the opening and closing cover and the standard position member are significantly warped, because a warping amount is significant, the position of the latent image writing unit with respect to the latent image-carrying members cannot be precisely decided even if the biasing unit causes the standard position member to touch the positioning unit. Due to this, the writing position accuracy of the latent image writing unit is reduced.